§ Mr. Austin Mitchell
To ask the Secretary of State for Transport if he will estimate the life expectancy of existing rail bridges and tunnels. 
§ Mr. Watts
Railtrack's route structures are preserved by ongoing maintenance and are rarely replaced in their entirety. Railtrack inspects its bridges and tunnels on a cyclical basis and maintains them as long as can be economically justified. Maintenance includes the replacement of component parts of the structure so that the life span of the entire structure is extended. Many bridges and tunnels dating from the very earliest days of railways in this country and abroad continue to give satisfactory service.